Development of Gum Tragacanth‐Based Graft Copolymer Hydrogel for the Adsorptive Removal of Dyes from Wastewater

This study presents the development of a polysaccharide‐based copolymer hydrogel with significant adsorption capacity toward dyes for application in the treatment of industrial effluents contaminated with dyes. The polysaccharide‐based graft copolymer has been made by microwave‐mediated free radical polymerization of co‐monomers, acrylamide (AAm) and itaconic acid (ITA), in the presence of the polysaccharide, gum tragacanth (GT). Methylene‐bis‐acrylamide (MBA) has been used as the crosslinking agent to facilitate the formation of a 3D network. The structure of the developed hydrogel was characterized using spectroscopic, physical, and morphological characterization techniques. Swelling studies carried out in aqueous media of pH 1.2, 7.4, and 9.0 revealed a pH‐responsive swelling behavior, with the highest swelling exhibited under pH 9.0 and the lowest at pH 1.2. The kinetic analysis of the swelling data indicated swelling to follow the pseudo‐second order kinetic model, and the diffusional exponent with a value less than 0.5 indicated a deviation from Fickian diffusion. The terpolymer gel was evaluated for the adsorption of ionic dyes using methylene blue (MB), crystal violet (CV), toluidine blue (TB), and indigo carmine (IC). Significant adsorption capacities of 312.5, 333.3, 357.14, and 232.55 mg g −1 toward MB, CV, TB, and IC, respectively, were observed. The Freundlich isotherm model described the adsorption isotherms well, and kinetic analysis of adsorption data demonstrated the adsorption to be a pseudo‐second‐order kinetic process. Thermodynamic analysis revealed the endothermic and spontaneous nature of adsorption. The primary binding forces involved in dye adsorption are proposed to be hydrogen bonding and electrostatic interactions. The reusability studies carried out in three adsorption‐desorption cycles demonstrated good performance of the material, confirming its potential for the treatment of wastewater in multiple cycles. Thus, the developed adsorbent is a promising candidate for the removal of dyes from an aqueous solution contaminated with ionic dyes.